Method of manufacturing external force detection sensor

ABSTRACT

A method of manufacturing an external force detection sensor in which a sensor element is formed by through-hole dry etching of an element substrate, and an electrically conductive material is used as an etching stop layer during the dry etching.

This application is a Divisional Application of U.S. patent applicationSer. No. 10/725,874 filed Dec. 2, 2003 now U.S. Pat. No. 7,049,165,which is a Divisional Application of U.S. patent application Ser. No.09/548,414 filed Apr. 13, 2000 now U.S. Pat. No. 7,067,344.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing an externalforce detection sensor, such as an angular velocity sensor and anacceleration sensor.

2. Description of the Related Art

FIG. 6A illustrates a top plan view of an angular velocity sensor whichis an external force detection sensor, and FIG. 6B illustrates a sectiontaken along the line A-A indicated in FIG. 6A. A sensor element 1 toconstitute the angular velocity sensor illustrated in FIG. 6A and FIG.6B is of predetermined shape in which an element substrate 3 (e.g., asemi-conductor substrate such as a single crystal silicon substrate) tobe joined with, for example, a glass support substrate 2 is dry-etched.

As illustrated in FIG. 6A and FIG. 6B, an oscillating body 5 is arrangedin a floating condition from the above-described support substrate 2above a surface 2 a which is a surface in the direction of the X-Y planeof the above-described support substrate 2. In the oscillating body 5, aweight 5 b is provided inside a frame body 5 a. A plurality of (four inan example in FIGS. 6A and 6B) fixed parts 6 are arranged on the supportsubstrate 2 in a fixed manner with intervals from each other, and theoscillating body 5 is supported in an oscillating manner In theX-direction and the Y-direction by each fixed part 6 through eachL-shaped support beam (beam) 7.

Comb-toothed movable electrodes 10 (10 a, 10 b) are formed on right andleft sides of the oscillating body 5 as viewed in FIG. 6A outwardly ineach direction of the X-axis, and fixed comb-toothed electrodes 11 (11a, 11 b) to be engaged with the movable electrodes 10 through clearanceare extended inward of fixed parts 12 in each direction of the X-axis.

An electrically conductive pattern not illustrated is connected to thecomb-toothed electrodes 11 a, 11 b, and the voltage is applied to thefixed comb-toothed electrodes 11 a, 11 b from each external side throughthe electrically conductive pattern. For example, when AC voltagesdifferent in phase by 180° are applied to the fixed comb-toothedelectrodes 11 a, 11 b through the electrically conductive pattern withthe movable electrodes 10 a, 10 b in the condition of a specified fixedvoltage (e.g., zero V), electrostatic forces opposite in direction toeach other are generated between the movable electrode 10 a and thefixed comb-toothed electrode 11 a, and between the movable electrode 10b and the fixed comb-toothed toothed electrode 11 b, and the oscillatingbody 5 is excitation-oscillated in the X-direction by the electrostaticforces.

Movable electrodes 13 (13 a, 13 b) are extended on upper and lower sidesof the oscillating body 5 as viewed in FIG. 6A in each longitudinaldirection, i.e., each direction of the Y-axis, and fixed electrodes 14(14 a, 14 b) opposite to the movable electrodes 13 through a clearanceare extended inward of a fixed part 15 in the longitudinal direction.

In the angular velocity sensor (external force detection sensor) of theabove-described constitution, a Coriolis force is generated in theY-direction when the external force detection sensor is rotated about aZ-axis orthogonal to the direction of the X-Y plane in a condition wherethe oscillating body 5 is excitation-oscillated in the X-direction asdescribed above. The Coriolis force is applied to the oscillating body5, and the oscillating body 5 is oscillated in the direction of theCoriolis force. The clearance between the above-described movableelectrodes 13 and fixed electrodes 14 is changed by the oscillation inthe Y-direction of the oscillating body 5 attributable to the Coriolisforce, and the electrostatic capacity between the movable electrodes 13and the fixed electrodes 14 is changed. The magnitude of the angularvelocity of the rotation can be detected by detecting the electricalsignal corresponding to the magnitude of the amplitude of theoscillation in the Y-direction of the oscillating body 5 generated bythe above-described Coriolis force making use of the change inelectrostatic capacity. Thus, the sensor element 1 of the angularvelocity sensor illustrated in FIGS. 6A and 6B forms a movable elementhaving a movable part such as the oscillating body 5 and a support beam7.

An example of a conventional method of manufacturing the angularvelocity sensor illustrated in FIGS. 6A and 6B is briefly describedreferring to FIG. 7A to FIG. 7E. For example, as illustrated in FIG. 7A,a recess 16 is formed on a back surface 3 b of the element substrate 3by a dry etching technology such as RIE (Reactive Ion Etching) to form,for example, a membrane (diaphragm) 17 of 60-70 pm in thickness d.

As illustrated in FIG. 7B, an etching stop layer 18 comprised of siliconoxide is formed on a top surface 16 a of the above-described recessedpart 16 using a film forming technology such as CVD (Chemical VaporDeposition).

As illustrated in FIG. 7C, the support substrate 2 is arranged on theback surface 3 b side of the above-described element substrate 3, thesupport substrate 2 and the element substrate 3 are heated to hightemperature, and a high voltage is applied thereto to anode-join thesupport substrate 2 with the element substrate 3.

After that, the membrane 17 of the above-described support substrate 2is machined making use of a photolithography method and RIE to form aplurality of through holes 20 reaching from the surface 3 a of theelement substrate 3 to the above-described etching stop layer 18 asillustrated in FIG. 7D, and the sensor element 1 is formed by formingthe oscillating body 5, the support beam 7, the movable electrode 10,the fixed comb-toothed electrode 11, the movable electrode 13, the fixedelectrode 14, etc. by a plurality of these through holes 20. In thisspecification and the claims, the dry etching technology to form thethrough holes to be passed from the face side to the back surface sideof the substrate is referred to as “through-hole dry etching”.

As described above, after the sensor element 1 is formed, the etchingstop layer 18 is removed by a wet etching process using a bufferhydrofluoric acid aqueous solution as illustrated in FIG. 7E. Theangular velocity sensor as illustrated in FIGS. 6A and 6B can thus bemanufactured.

The etching stop layer 18 to be formed in manufacturing the externalforce detection sensor such as the angular velocity sensor has to beconventionally formed of an insulating material such as silicon oxidefrom the viewpoint of facilitation of forming a layer and simplificationof a manufacturing process of the external force detection sensor.However, the inventor noticed that a notch (a profile distortion) isformed on a lower part side (i.e., a side on which the etching stoplayer 18 is formed) of a side wall surface of the through holes 20 asillustrated in FIG. 7E since the etching stop layer 18 is formed of theinsulating material as described above.

This may be considered attributable to the following reason. Forexample, when the element substrate 3 is machined by through-hole dryetching to form the sensor element 1, the etching removal is achievedfaster in a hole larger in etching removal area such as a through hole20 a between the frame body 5 a and the weight 5 b of the oscillatingbody 5 illustrated in FIG. 6A than in a hole smaller in etching removalarea such as a through hole (an etching groove) 20 a between the movableelectrode 10 and the fixed comb-toothed electrode 11 by themicro-loading effect.

The time required to achieve the etching removal up to the etching stoplayer 18 and complete the forming of the through holes 20 after thethrough-hole dry etching is started is different for each through hole20 by the difference in the above-described etching removal area. Sincethe above-described through-hole dry etching is continuously performeduntil the forming of all through holes 20 is completed, some throughholes 20 which are continuously exposed to an etching gas though theetching removal is completed are generated (hereinafter, these throughholes are referred to as the “over etched through holes”).

The etching gas continuously enters such over etched through holes 20during the over-etching, and the etching stop layer 18 at a bottom partof these over etched through holes 20 is charged positive by thecollision of the positive ion in the etching gas.

When the etching is continued even after the etching stop layer 18 ischarged positive and the etching gas continuously enters inside the overetched through holes 20, the positive ion in the etching gas is advancedstraight toward the etching stop layer 18 inside the through holes 20,but repulsed by chef positive charge of the above-described etching stoplayer 18 immediately before the positive ion reaches the etching stoplayer 18. In addition, the side wall surface of the over etched throughholes 20 is charged negative by the collision of the electron in theetching gas, and thus, the above-described positive ion is attracted tothe side wall surface of the through holes 20 immediately before itreaches the etching stop layer 18, and the course of the positive ion islargely curved. As a result, the positive ion in the etching gascollides with the bottom side (the side on which the etching stop layer18 is formed) of the side wall surface of the through hole 20 to formthe notch n as illustrated in FIG. 7E.

Since the etching stop layer 18 is formed of the insulating material, itis found that the following problem can occur. When no through holes 20are completed yet while the through hole dry etching is performed toform the through holes 20, as shown in FIG. 8A, the heat generated inthe side wall surface of the through holes 20 (as shown by the arrows inFIG. 8A) is diffused into the membrane 17, and the area to be dry-etchedof the membrane 17 or the like is heated to the same temperature almostover the whole area.

However, when through holes 20A are generated during the over etching asillustrated in FIG. 8B, the temperature of a part between the overetched through holes 20A (for example, a hole indicated by the referencenumeral 21 in FIG. 8B) rises. That is, when the electrons in the etchinggas collide with the side wall surface of the through hole 20A duringthe over etching to generate heat, the hole 21 is thermally independentfrom other areas since the etching stop layer 18 is formed of theinsulating material and its heat conductivity is very inferior, the heatis stored in the side wall surface of the hole 21, and the temperatureof the hole 21 rises higher than the other areas. Thus, the hole 21becomes easier to etch than the other areas, the etching removal isexcessively achieved as indicated by a solid line while the true etchingremoval should be originally achieved to the dimension as indicated by abroken line in FIG. 8C, resulting in a part not being formed to thedesigned dimension because of the excessive etching.

As described above, the inventor noticed that the notch n is formed onthe etching stop layer 18 side of the side wall surface of the throughholes 20, excessive etching is generated, and the sensor element 1cannot be formed to the designed dimension with excellent accuracy sincethe etching stop layer 18 has been formed of the insulating material ina conventional practice. For example, since the sensor element 1 can notthus be formed with excellent dimensional accuracy, stable outputsensitivity of the external force detection sensor can not be obtained.

SUMMARY OF THE INVENTION

Accordingly, the present invention can solve the problem associated withthe conventional arc and provides a manufacturing method of an externalforce detection sensor capable of forming a sensor element to thedesigned dimension with excellent accuracy.

To achieve the above-described purpose, the present invention, inaccordance with a first aspect, uses an electrically conductive materialas an etching stop layer during dry-etching of the above-describedelement substrate.

The method of manufacturing the external force detection sensoraccording to a second aspect of the present invention is characterizedin including a process in which a recessed part is formed on a backsurface side of the element substrate and a membrane is formed on a faceside, a process in which an etching-stop layer comprised of theelectrically conductive material is provided on a top surface of therecessed part of the above-described element substrate, a process inwhich the back surface side of the element substrate is joined with asupport substrate, and a process in which a sensor element is formed bydry-etching the membrane of the above-described element substrate.

According to a third aspect of the invention, the manufacturing methodof manufacturing the external force detection sensor is characterized inthat the recessed part to constitute the above-described secondinvention is formed in a center part of the back surface of the elementsubstrate.

According to a fourth aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the etching stop layer comprised of the electrically conductivematerial is interposed between the above-described element substrate anda dummy support substrate to support this element substrate in themanufacturing method of the external force detection sensor to form thesensor element by effecting the through-hole dry etching of the elementsubstrate.

According to a fifth aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the constitution of the above-described fourth aspect is provided,and after the sensor element is formed on the element substrate, thedummy support substrate and the etching stop layer are removed, andthen, the support substrate with the recessed part formed therein isarranged on a back surface side of the element substrate to arrange therecessed part of the above-described support substrate opposite to thesensor element of the above-described element substrate, and the supportsubstrate is joined with the element substrate.

According to a sixth aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the etching stop layer comprised of the electrically conductivematerial is formed in a set sensor element forming area on the backsurface side of the element substrate, the support substrate with therecessed part formed therein is arranged on the back surface side of theelement substrate to arrange the recessed part of the support substrateopposite to the etching stop layer of the element substrate, the supportsubstrate is joined with the element substrate, and then, the sensorelement forming area of the above-described element substrate ismachined by the through-hole dry-etching from the face side to form thesensor element.

According to a seventh aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the etching stop layer comprised of the electrically conductivematerial is formed in the set sensor element forming area on the backsurface side of the element substrate, the support substrate with therecessed part formed therein is arranged on the back surface side of theabove-described element substrate to arrange the recessed part in theabove-described support substrate opposite to the etching stop layer ofthe above-described element substrate, and then, the support substrateis joined with the element substrate, and then, the thickness of theabove-described element substrate is reduced to a specified value, andthen, the sensor element forming area of the above-described elementsubstrate is machined by through-hole dry-etching from the face side toform the sensor element.

According to an eighth aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the set sensor element forming area or the element substrate ismachined from both face and back surface sides to form a membrane, theetching stop layer comprised of the electrically conductive material isformed on the back surface side of the membrane, and then, the supportsubstrate is joined with the back surface side of the element substrate,and the membrane is machined by the through-hole dry-etching from theface side to form the sensor element.

According to a ninth aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the invention to constitute the above-described second, third,fifth, sixth, seventh or eighth aspect is formed of a silicon, thesupport substrate is formed of a glass material, and the elementsubstrate and the support substrate are anodically joined with eachother.

According to a tenth aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the constitution of either one of the above-described first toninth aspects is provided, and the etching stop layer is formed of theelectrically conductive material in which the etch selectivity, i.e.,the ratio of the dry-etch rate of the element substrate to the dry-etchrate of the etching stop layer is not less than 1.

According to an eleventh aspect of the invention, the method ofmanufacturing the external force detection sensor is characterized inthat the sensor element to constitute either of the above-describedfirst to tenth aspects is a movable element.

In the present invention, the etching stop layer is formed of theelectrically conductive material, and thus, even when the positive ionin the etching gas entering inside the through holes during theover-etching operation collides with the etching stop layer to chargethe etching stop layer positive while the through holes are formed inthe element substrate by through-hole dry etching, the positive chargein the etching stop layer is instantaneously and electricallyneutralized by the negative charge on the side wall surface of thethrough holes, and the positively charged condition of the etching stoplayer is eliminated and not continuous.

Thus, almost all positive ions in the etching gas entering inside thethrough holes during the over-etching operation are advanced straighttoward the etching stop layer, and prevented from colliding with theside wall surface of the through holes. The notch forming in the sidewall surface of the through holes can be avoided thereby.

Further, since the etching stop layer is formed of electricallyconductive material and its heat conductivity is excellent, the etchingstop layer can function as a heat transfer passage, and the temperatureof the area to be etched can be substantially uniform almost over thewhole area, and the excessive etching attributable to non-uniformtemperature can be prevented.

As described above, by forming the etching stop layer of electricallyconductive material, both the notch forming in the side wall surface ofthe through holes and the excessive etching can be avoided. The sensorelement can be manufactured as designed with excellent dimensionalaccuracy thereby. Thus, the external force detection sensor excellent insensitivity, stable in output sensitivity and reliable in quality can beprovided.

In a method of manufacturing the external force detection sensor wherethe recessed part is provided in the back side of the element substrateto form the membrane, and the above-described membrane is machined bythrough-hole dry etching to form the sensor element, where the dummysupport substrate is joined with the element substrate, and theabove-described element substrate is machined by the through-hole dryetching to form the sensor element, where the etching stop layer isformed in the preset sensor element forming area on the back side of theelement substrate, the support substrate with the recessed part formedtherein is joined with the above-described element substrate, and theabove-described membrane is machined by the through-hole dry etching toform the sensor element, or where the recessed part is formed on boththe face and back sides of the element substrate to form the membrane,and the above-described membrane is machined by the through-hole dryetching to form the sensor element, the sensor element is very fine insize, and it is not easy to form the sensor element with excellentdimensional accuracy. However, by using the present invention, itbecomes easy to manufacture the sensor element as designed withexcellent dimensional accuracy even if it is very fine, and the sensorelement is very effective to manufacture the external force detectionsensor compact in size and excellent in performance.

In a method of manufacturing the external force detection sensor wherethe etching stop layer is formed in the preset sensor element formingarea on the back side of the element substrate, the support substratewith the recessed part formed therein is joined with the above-describedelement substrate, the element substrate is machined thin to thespecified thickness, and the above-described membrane is machined by thethrough-hole dry etching to form the sensor element, the thin elementsubstrate can be protected by the support substrate during themanufacture, the breakage of the element substrate can be prevented, andthe yield of the external force detection sensor can be improved.

In a manufacturing method where the element substrate is formed ofsilicon, the support substrate is formed of a glass material, and theelement substrate is anodically joined with the support substrate, theelement substrate can be firmly joined with the support substrate toimprove the mechanical reliability of the external force detectionsensor.

When the sensor element is a movable element, stricter dimensionalaccuracy is required, and the stricter requirements can be sufficientlycoped with by using the present invention, whereby a sensor elementwhich is a movable element excellent in characteristic can bemanufactured, and an external force detection sensor excellent insensitivity and stable in output sensitivity can be provided.

In addition, when the etching stop layer is formed of the electricallyconductive material which is not less than 1 in etch selectivity whichis the ratio of the dry etch rate of the element substrate to the dryetch rate of the etching stop layer, a condition where holes are formedin the etching stop layer during the dry etching can be avoided.

For the purpose of illustrating the invention, there is shown in thedrawings several forms which are presently preferred, it beingunderstood, however, that the invention is not limited to the precisearrangements and instrumentalities shown.

Other features and advantages of the present invention will becomeapparent from the following description of the invention which refers tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1E are views illustrating a first embodiment of a method ofmanufacturing an external force detection sensor of the presentinvention;

FIGS. 2A to 2E are views illustrating a second embodiment;

FIGS. 3A to 3D are views illustrating a third embodiment;

FIGS. 4A to 4E are views illustrating a fourth embodiment;

FIGS. 5A to 5E are views illustrating a fifth embodiment;

FIGS. 6A and 6B are views illustrating an example of the external forcedetection sensor;

FIGS. 7A to 7E are views illustrating an example of a conventionalmethod of manufacturing the external force detection sensor; and

FIGS. 8A to 8C are views illustrating conventional problems.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

Hereinafter, the preferred embodiments of the present invention areexplained in detail with reference to the drawings.

The embodiments of the present invention are described referring to thedrawings.

FIG. 1A to FIG. 1E illustrate a first embodiment of a manufacturingmethod of an external force detection sensor of the present invention.In the explanation of the first embodiment, the same symbol is given tothe same component in the above-described conventional example, and theduplicate explanation of common parts is omitted.

The first embodiment is characterized in that an etching stop layer 18formed in manufacturing a sensor element 1 to constitute the externalforce detection sensor is formed of an electrically conductive material.Other constitutions are same as those in the above-describedconventional example.

Recently, higher sensitivity has been demanded for the external forcedetection sensor such as an angular velocity sensor, and it is desiredto manufacture the sensor element 1 with more excellent dimensionalaccuracy. Thus, a notch n and excessive etching formed on a side wallsurface of a through hole 20 have raised a serious problem as describedabove. In a conventional practice as described above, the etching stoplayer 18 has been formed of an insulating material from the viewpoint offacilitation in forming the layer and simplification of themanufacturing process, and no consideration has been given to formingthe etching stop layer 18 of other materials. However, to solve theabove-described problem, in accordance with the present invention, theetching stop layer 18 is formed of a electrically conductive material.

That means, in this first embodiment, as indicated in FIG. 1A, arecessed part 16 is formed on a back surface 3 b of an element substrate3 to form a membrane 17 of a specified thickness d (e.g., 70 μm). Asindicated in FIG. 1B, the etching stop layer 18 is formed on a topsurface 16 a (a back surface side of the membrane 17) of the recessedpart 16. In this first embodiment, as described above, the etching stoplayer 18 is formed of an electrically conductive material, and theetching stop layer 18 is formed on the top surface 16 a of theabove-described recessed part 16 by, for example, electron beamevaporation method or film forming technology such as sputtering. Inthis first embodiment, the electrically conductive material to form theetching stop layer 18 is not less than 1 in etch selectivity (i.e., theratio of the dry etch rate of the element substrate 3 to the dry etchrate of the etching stop layer 18) in order to surely perform thefunction as the etching stop layer.

Next, as indicated in FIG. 1C, the support substrate 2 is arranged on aback surface 3 b side of the element substrate 3, and the supportsubstrate 2 and the element substrate 3 are anodically joined with eachother. As indicated in FIG. 1D, the through-hole dry etching of themembrane 17 of the element substrate 3 is effected from the face 3 aside making use of photolithography and dry-etching technology such asRIE to form a plurality of through holes 20 reaching the above-describedetching stop layer 18, and the sensor element 1 as illustrated in FIG. 6is formed by a plurality of through holes 20.

In effecting the above-described through-hole dry etching, duringover-etching operation, an etching gas enters inside the through holes20, and the positive ion in the etching gas collides with the etchingstop layer 18, and the etching stop layer 18 is charged positive. Sincethe etching stop layer 18 is formed of electrically conductive material,the positive charge in the etching stop layer 18 is instantaneously andelectrically neutralized by the negative charge on the side wall surfaceof the through holes 20 to eliminate the positively charged condition ofthe etching stop layer 18.

In the through holes 20 during the over-etching operation, the positiveions in the etching gas enter are advanced straight toward the etchingstop layer 18, and collide with the etching stop layer 18, preventing aproblem in a conventional practice that the course of the positive ionsis curved (attributable to the etching stop layer 18 which iscontinuously charged positive), and thereby collide with the side wallsurface of the through holes 20 to form a notch n in the side wallsurface.

Further, in this first embodiment, the etching stop layer 18 is formedof electrically conductive material which is excellent in thermalconductivity, as described above, and can function as a heat transferpassage. Thus, even when a part surrounded by the through holes 20generates heat because of the collision of the etching gas, the heat istransferred to other areas through the etching stop layer 18, and thetemperature of essentially the whole area to be etched can be set atessentially the same temperature. Excessive etching attributable tonon-uniform temperature can be avoided thereby.

As described above, the notch n preventive effect of the side wallsurface of the through holes 20 and the excessive etching avoidingeffect attributable to the non-uniform temperature can be demonstratedby forming the etching stop layer 18 of the electrically conductivematerial. In particular, based on experiments by the inventor, theabove-described effects are remarkable and preferable when theelectrically conductive material of the etching stop layer is not lessthan 1×10⁶ Ω⁻¹·m⁻¹ in electric conductivity and not less than 0.1W·cm⁻¹·K⁻¹ in heat conductivity. For example, the etching stop layer 18may be optimally formed of titanium (1.7×10⁶ Ω⁻¹·m⁻¹ in electricconductivity and 0.219 W·cm⁻¹·K⁻¹ in heat conductivity) or aluminum(3.8×10⁷ Ω⁻¹·m⁻¹ in electric conductivity and 2.37 W·cm⁻¹·K⁻¹ in heatconductivity).

Nickel or copper, etc. may, of course, be used for the electricallyconductive material of the etching stop layer 18. The thickness of theetching stop layer 18 is appropriately set considering the kind ofelectrically conductive material used to form the etching stop layer 18and the thickness of the membrane 17, and, for example, when the etchingstop layer 18 is formed of titanium or aluminum, the etching stop layer18 is formed to approximately 300 μm in thickness.

After the specified forming of all through holes 20 is completed by thethrough-hole dry etching, the etching stop layer 18 formed of theabove-described electrically conductive material is removed by a wetetching process as indicated in FIG. 1E with, for example, hydrofluoricacid aqueous solution. The above-described hydrofluoric acid aqueoussolution removes the etching stop layer 18 of the electricallyconductive material by a wet etching process, but the element substrate3 is not damaged thereby.

As described above, after the etching stop layer 18 is removed by a wetetching process, a lid part 30 as indicated by a broken line in FIG. 1Eas necessary. In such a case, for example, a glass substrate which isthe lid part 30 with a recessed part 31 formed therein, is arranged on aface side of the element substrate 3 indicated in FIG. 1E, and therecessed part 31 of the above-described glass substrate 30 is arrangedopposite to the sensor element 1 of the element substrate 3, and theelement substrate 3 is lapped on the glass substrate 30 so as to beanodically joined with each other. When the lid part 30 is thusprovided, the sensor element 1 is stored and sealed in an internal spaceto be formed by the support substrate 2 and the lid part 30, and theinternal space can be evacuated according to the operationalcharacteristic of the sensor element 1.

In this first embodiment, the external force detection sensor ismanufactured by the above-described manufacturing method.

In this first embodiment, the etching stop layer 18 is formed of theelectrically conductive material, and the etching stop layer 18 at abottom part of the through holes 20 under the over-etching operation canbe prevented from being continuously charged positive during thethrough-hole dry etching, and the notch n forming of the side wallsurface of the through holes 20 attributable to the continuouspositive-charge of the etching stop layer 18 can be avoided. Since theetching stop layer 18 formed of the electrically conductive material canfunction as a heat transfer passage, the heat is transferred through theetching stop layer 18, and the temperature can be maintainedapproximately the same over almost all of the area to be etched, and theexcessive etching attributable to the non-uniform temperature can beprevented.

As described above, since both the notch n forming and the excessiveetching can be prevented, the sensor element 1 can be manufactured withexcellent dimensional accuracy, the external force detection sensorexcellent in sensitivity and stable in output sensitivity can beprovided, and the reliability of the quality of the external forcedetection sensor can be improved.

Further, in this first embodiment, the etching stop layer 18 is formedof the electrically conductive material in which the above-describedetch selectivity is not less than 1, and there is hardly a problem thatthe etching stop layer 18 is subjected to the etching removal during thethrough-hole dry etching and that holes are formed in the etching stoplayer 18. Even if holes are formed in the etching stop layer 18, theetching stop layer 18 is formed almost over the whole area of the topsurface 16 a of the recessed part 16 in this first embodiment, and thetop surface 16 a of the recessed part 16 can be prevented from beingdamaged by the etching gas entering inside the recessed part 16 fromholes in the above-described etching stop layer 18.

As indicated in the above-described first embodiment, the etching stoplayer 18 is formed of the electrically conductive material, and thusvarious changes must be given to the conventional manufacturing process,which one skilled in the art would appreciate and, accordingly, thedetailed explanation of such changes is omitted here.

A second embodiment is described below. In the explanation of the secondembodiment, the same symbol is given to the same component in theabove-described first embodiment, and the duplicate explanation ofcommon parts is omitted.

FIG. 2A to FIG. 2E illustrate the second embodiment of the manufacturingmethod of the external force detection sensor of the present invention.In this second embodiment, firstly as indicated in FIG. 2A, the etchingstop layer 18 is formed almost over the whole area of the back surface 3b of the element substrate 3 by film forming technology such assputtering. Also in this second embodiment, the etching stop layer 18 isformed of electrically conductive material similar to that in theabove-described embodiment.

As indicated in FIG. 2B, a dummy support substrate 25 is attached to theback surface 3 b side of the above-described element substrate 3 throughthe above-described etching stop layer 18 and an adhesive layer (e.g.,photo resist) 23.

After that, as indicated in FIG. 2C, a plurality of through holes 20leading to the etching stop layer 18 from the face 3 a side of theelement substrate 3 are formed by through-hole dry etching to form thesensor element 1 as illustrated in FIG. 6.

A coupled body of the above-described element substrate 3 with the dummysupport substrate 25 is immersed in acetone solution, etc. to dissolvethe adhesive layer 23, and the dummy support substrate 25 is separatedfrom the element substrate 3. Then, as indicated in FIG. 2D, the etchingstop layer 18 formed of the above-described electrically conductivematerial is removed by a wet etching process using an aqueous solutionsuch as hydrofluoric acid aqueous solution.

After that, as indicated in FIG. 2E, the glass support substrate 2 withthe recessed part 26 formed therein is arranged on the back surface 3 bside of the element substrate 3, the recessed part 26 of theabove-described support substrate 2 is arranged opposite to the sensorelement 1 of the element substrate 3, and the support substrate 2 isanodically joined with the element substrate 3. Further, the lid part 30illustrated in the above-described first embodiment may besimultaneously anodically joined with the face side of the elementsubstrate 30 as necessary. The recessed part 26 of the above-describedsupport substrate 2 is provided not to prevent the above-describedsensor element 1 from being moved.

Also in this second embodiment, the etching stop layer 18 is formed ofelectrically conductive material similar to that in the above-describedfirst embodiment, and thus, the etching stop layer 18 is prevented frombeing continuously charged positive, and the notch n forming on the sidewail surface of the through holes 20 can be avoided, non-uniformtemperature in the area to be etched can be prevented, and the excessiveetching attributable to the uniform temperature can be avoided. Thus,the sensor element 1 can be manufactured with excellent dimensionalaccuracy, and the external force detection sensor excellent insensitivity and stable in output sensitivity can be provided.

A third embodiment is described below. In the explanation of the thirdembodiment, the same symbol is given to the same component in theabove-described respective embodiments, and the duplicate explanation ofcommon parts is omitted.

FIG. 3A to FIG. 3D illustrate the third embodiment of the manufacturingmethod of the external force detection sensor. In this third embodiment,firstly as indicated in FIG. 3A, the etching stop layer 18 is formed ina preset sensor element forming area R (i.e., an area to form the sensorelement 1 indicated in FIG. 6A) on the back surface 3 b of thesemi-conductor element substrate 3. Also in this third embodiment, theetching stop layer 18 is formed of electrically conductive materialsimilar to that in the above-described first and second embodiments, andthe etching stop layer 18 is formed on the back surface 3 b side of theelement substrate 3 by electron beam evaporation method and film formingtechnology such as sputtering similar to the above-described first andsecond embodiments.

As indicated in FIG. 3B, the glass support substrate 2 with the recessedpart 26 Formed therein is arranged on the back surface 3 b side of theelement substrate 3, the recessed part 26 of the support substrate 2 isarranged opposite to the etching stop layer 18 of the element substrate3, and the support substrate 2 is anodically joined with the elementsubstrate 3.

After that, as indicated in FIG. 3C, the sensor element forming area Ris worked from the face 3 a side of the element substrate 3 bythrough-hole dry etching to form a plurality of through holes 20 leadingto the etching stop layer 18, and the sensor element 1 as indicated inFIG. 6A is formed. Then, as indicated in FIG. 3D, the etching stop layer18 is removed by the method similar to that in the above-described firstand second embodiments. Then, the lid part 30 described in the firstembodiment may be anodically joined with the face side of the elementsubstrate 30, as necessary. The external force detection sensor is thusmanufactured.

Also in this third embodiment, the etching stop layer 18 is formed ofelectrically conductive material similar to the above-described firstand second embodiments, and thus, both the notch n forming in the sidewall surface of the through holes 20 and the excessive etching can beavoided to form the sensor element 1 to the designed dimensions. Thus,the external force detection sensor excellent in sensitivity and stablein output sensitivity can be provided.

A fourth embodiment is described below. In the explanation of the fourthembodiment, the same symbol is given to the same component in theabove-described respective embodiments, and the duplicate explanation ofcommon parts is omitted.

FIG. 4A to FIG. 4E illustrate the fourth embodiment of the manufacturingmethod of the external force detection sensor. In this fourthembodiment, the external force detection sensor is manufactured by themanufacturing process approximately similar to the above-described thirdembodiment, but the fourth embodiment is differently characterized inthat after the glass support substrate 2 is anodically joined with thesemi-conductor element substrate 3 as indicated in FIG. 4B, the elementsubstrate 3 is reduced in thickness by the etching or cutting to apredetermined value as indicated in FIG. 4C, and a plurality of throughholes 20 are formed in the element substrate 3 by through-hole dryetching to form the sensor element 1.

In this fourth embodiment, the etching stop layer 18 is formed ofelectrically conductive material similar to the above-described firstand third embodiments, and thus, both the notch n forming in the sidewall surface of the through holes 20 and the excessive etching can beavoided, the sensor element 1 can be formed with excellent dimensionalaccuracy, and the external force detection sensor excellent insensitivity and stable in output sensitivity can be provided.

When the thin-machined element substrate 3 is handled in a single bodycondition in manufacturing the external force detection sensor, the thinsingle element substrate 3 is easy to break, including cracking andpartly chipping. To cope with this, in this fourth embodiment, thesupport substrate 2 is joined with the element substrate 3 before theelement substrate 3 is formed thin, and then, the element substrate 3 isformed thin. Thus, the thin element substrate 3 is not handled in asingle body condition, and the breakage of the element substrate 3during the manufacture can be prevented. Further, a very precisehandling device can be dispensed with to manufacture the external forcedetection sensor.

A fifth embodiment is described below. In the explanation of the fifthembodiment, the same symbol is given to the same component in theabove-described respective embodiments, and the duplicate explanation ofcommon parts is omitted.

FIG. 5A to FIG. 5E illustrate the fifth embodiment of the manufacturingmethod of the external force detection sensor. In this fifth embodiment,firstly as indicated in FIG. 5A, recessed parts 27, 28 are formed in apreset sensor element forming area R on both the face side 3 a and theback surface 3 b of the semi-conductor element substrate 3 to form themembrane 17.

Next, as indicated in FIG. 5B, the etching stop layer 18 is formed onthe back side of the above-described membrane 17. Also in this fifthembodiment, the etching stop layer 18 is formed of electricallyconductive material similar to the above-described first and fourthembodiments.

After that, the glass support substrate 2 is anodically joined with theback surface 3 b side of the element substrate 3 as indicated in FIG.5C, and as indicated in FIG. 5D, a plurality of through holes 20 areformed by through-hole dry etching of the membrane 17 from its face sideto form the sensor element 1 as indicated in FIG. 6. Then, as indicatedin FIG. 5E, the etching stop layer 18 is removed by a method similar tothat in the above-described first and fourth embodiments to form thesensor element 1. Then, the lid part 30 may be provided on the face sideof the element substrate 3 similar to the above-described first andfourth embodiments. The external force detection sensor can bemanufactured as described above.

Also in this fifth embodiment, the etching stop layer 18 is formed ofelectrically conductive material similar to the above-described firstand fourth embodiments, and thus, both the notch n forming in the sidewall surface of the through holes 20 and the excessive etching can beavoided, the sensor element 1 can be formed to the designed dimensions,and the sensitivity and the stability in the output sensitivity of theexternal force detection sensor can be improved.

The present invention is not limited to the above-described respectiveembodiments, but can be of various embodiments. For example, in theabove-described embodiments, the element substrate 3 is not cooledduring the dry etching, but the element substrate 3 may be cooled duringthe dry etching. When the etching stop layer 18 is formed of theinsulating material like a conventional practice, the above-describedproblem of non-uniform temperature arises even if the whole elementsubstrate 3 is cooled during the through-hole dry etching. On the otherhand, by forming the etching stop layer 18 of electrically conductivematerial, similar effect to that in the above-described embodiments canbe obtained even when the element substrate 3 is cooled during thethrough-hole dry etching.

Further, in the above-described second embodiment, the element substrate3 is joined with the dummy support substrate 25 through the etching stoplayer 18 and the adhesive layer 23, but when the etching stop layer 18is formed of an electrically conductive adhesive, such as anelectrically conductive resin, the etching stop layer 18 can function asthe adhesive layer, and the above-described adhesive layer 23 may bedispensed with.

In addition, in the above-described embodiments, the support substrate 2is formed of a glass material, but the material of the support substrate2 is not so limited and may be formed of silicon or other materials.

Further, in the above-described embodiments, the etching stop layer 18is formed of electrically conductive material whose etch selectivity isnot less than 1, but when the thickness of the etching stop layer 18 isincreased, it may be formed of electrically conductive material whoseetch selectivity is less than 1.

In addition, explanation of the invention has been given with respect tothe angular velocity sensor illustrated in FIGS. 6A and 63 as anexample, but, of course, the present invention is applicable to variousexternal force detection sensors other than the angular velocity sensorillustrated in FIGS. 6A and 6B, such as an acceleration sensor.

While preferred embodiments of the invention have been disclosed,various modes of carrying out the principles disclosed herein arecontemplated as being within the scope of the following claims.Therefore, it is understood that the scope of the invention is not to belimited except as otherwise set forth in the claims.

1. A method of manufacturing an external force detection sensor,comprising the steps of: providing an element substrate including afront surface side and a back surface side having a sensor elementforming area; forming an etching stop layer of a conductive materialonly in the sensor element forming area of the back surface side of theelement substrate; arranging a support substrate with a recessed portiontherein on the back surface side of said element substrate, the recessedportion being arranged opposite to the etching stop layer of saidelement substrate; joining the support substrate to the elementsubstrate; through-hole dry etching the front surface side of theelement substrate until reaching the etching stop layer so as to form asensor element.
 2. The method of manufacturing an external forcedetection sensor according to claim 1, further comprising the step ofreducing a thickness of the element substrate after the step of joiningthe support substrate to the element substrate and before the step ofthrough-hole dry etching the front surface side of the elementsubstrate.
 3. The method of manufacturing an external force detectionsensor according to claim 1, wherein the element substrate includes asilicon material.
 4. The method of manufacturing an external forcedetection sensor according to claim 2, wherein the element substrateincludes a silicon material.
 5. The method of manufacturing an externalforce detection sensor according to claim 1, wherein the supportsubstrate includes a glass material.
 6. The method of manufacturing anexternal force detection sensor according to claim 2, wherein thesupport substrate includes a glass material.
 7. The method ofmanufacturing an external force detection sensor according to claim 1,wherein the step of joining the support substrate to the elementsubstrate includes a step of anodically joining the support substrate tothe element substrate.
 8. The method of manufacturing an external forcedetection sensor according to claim 2, wherein the step of joining thesupport substrate to the element substrate includes a step of anodicallyjoining the support substrate to the element substrate.
 9. The method ofmanufacturing an external force detection sensor according to claim 1,wherein an etching selectivity of the conductive material has a ratio ofa dry etching rate of the element substrate to a dry etching rate of theetching stop layer of at least
 1. 10. The method of manufacturing anexternal force detection sensor according to claim 2, wherein an etchingselectivity of the conductive material has a ratio of a dry etching rateof the element substrate to a dry etching rate of the etching stop layerof at least
 1. 11. The method of manufacturing an external forcedetection sensor according to claim 1, wherein the sensor element is amovable element.
 12. The method of manufacturing an external forcedetection sensor according to claim 2, wherein the sensor element is amovable element.
 13. The method of manufacturing an external forcedetection sensor according to claim 1, wherein the conductive materialof the etching stop layer is electrically conductive.
 14. The method ofmanufacturing an external force detection sensor according to claim 2,wherein the conductive material of the etching stop layer iselectrically conductive.